A consultant's perspective on the use of bitumen-rubber in especially double seals

Abstract

Paper presented at the 30th Annual Southern African Transport Conference 11-14 July 2011 "Africa on the Move", CSIR International Convention Centre, Pretoria, South Africa.

In life-cycle assessments conducted over the past 25 years, bitumen-rubber has proven itself as the most cost-effective modified binder in the South African bituminous product spectrum. It has been proven that by using bitumen-rubber, the life cycle cost decreases significantly whilst effectively increasing the functional performance and salvaging the otherwise rapidly deteriorating South African roads. The deterioration of the South African road network IS considered to be primarily the result of a lack of timely maintenance intervention on the ageing existing infrastructure. In order to retain the performance properties of the bitumen-rubber blend, South African roads engineers have adopted design methods and construction techniques to ensure that only minimal cutter is added to the bitumen-rubber blend before application (this does not apply to winter-grade applications). The objective of this paper is to present case studies and performance of unusual projects where bitumen-rubber was used successfully in single and double seals in order to demonstrate how the design parameters were extended. A brief overview is given of the properties and manufacture of bitumen-rubber, whlch is common to the projects whlch will then be discussed. These case studies will demonstrate that although bitumen-rubber single seals provide a useful action on badly deteriorated roads, bitumenrubber double seals are more cost-effective and have a longer life.